Wide-band RF signal power detecting element and power detecting device using the same

ABSTRACT

A wide-band RF signal power detecting element includes, on an insulating substrate ( 21 ), at least one thin-film resistor ( 22   a ) for absorbing the power of a signal to be measured and generating heat, first and second ground electrodes ( 27, 28 ) formed by thin-film conductors, a first thin-film connecting portion ( 24 ) for electrically connecting the first ground electrode ( 27 ) to the thin-film resistor ( 22   a ), a second thin-film connecting portion ( 25 ) for electrically connecting the second ground electrode ( 28 ) to the thin-film resistor ( 22   a ) and narrowing the gap between the first and second thin-film connecting portions ( 24, 25 ) toward the thin-film resistor ( 22   a ), and an input electrode ( 26 ) formed between the first and second ground electrodes ( 27, 28 ) and electrically connected to the thin-film resistor ( 22   a ).

[0001] This application is a Division of Application Ser. No. 09/462,653filed Jan. 11, 2000.

TECHNICAL FIELD

[0002] The present invention relates to a power detecting element fordetecting the power of a wide-band RF signal and a power detectingdevice using the same and, more particularly, to a wide-band RF signalpower detecting element which has an improved frequency characteristicand can be easily manufactured, and a power detecting device using thesame.

BACKGROUND ART

[0003] As is well known, to detect the power of a RF signal over a wideband, it is possible to use a diode detecting system which detects asignal by using a diode and a thermocouple system which allows aresistor to absorb a signal and detects heat generated by the resistorby using a thermocouple.

[0004] The diode detecting system has the advantage that a response isobtained with almost no delay when an input signal is supplied to thediode.

[0005] This diode detecting system, however, has the problem that thedetection accuracy is low because the system is readily influenced bythe signal waveform and the signal level.

[0006] Additionally, the junction capacitance of the diode makes itdifficult for the diode detecting system to detect the power of a RFsignal of millimeter waves or more.

[0007] On the other hand, the thermocouple system cannot achieve suchhigh-speed responses as in the diode detecting system, because heat isgenerated by supplying a signal to the resistor. This thermocouplesystem, however, has the advantage that the system can accurately detectthe power of a signal without being influenced by the signal waveform.

[0008] The present applicant has disclosed a power detector (element)and a power detecting device using this thermocouple system inInternational Publication No. WO88/03319 (Japanese Patent ApplicationNo. 62-506672).

[0009] As shown in FIG. 20, this power detector includes a firstthermocouple 4A and a second thermocouple 4B formed on an insulatingsubstrate 1. The first thermocouple 4A is formed by connecting a metalthin-film conductor 3A to a silicon germanium mixed-crystal thin film2A. The second thermocouple 4B is formed by connecting a metal thin-filmconductor 3B to a silicon germanium mixed-crystal thin film 2B.

[0010] In this structure, the silicon germanium mixed-crystal thin filmof the first thermocouple 4A and the metal thin-film conductor 3B of thesecond thermocouple 4B are formed parallel to oppose each other.

[0011] End portions of the silicon germanium mixed-crystal thin film 2Aof the first thermocouple 4A and the metal thin-film conductor 3B of thesecond thermocouple 4B are connected by a first electrode 5.

[0012] A second electrode 6 is connected to the metal thin-filmconductor 3A of the first thermocouple 4A.

[0013] A third electrode 7 is connected to the silicon germaniummixed-crystal thin film 2B of the second thermocouple 4B.

[0014] The electromotive forces of the first and second thermocouples 4Aand 4B are added and output to between the second and third electrodes 6and 7.

[0015] Beam lead electrodes 8, 9, and 10 for decreasing the thermalresistance in a cold junction between the first and second thermocouples4A and 4B are connected to the first, second, and third electrodes 5, 6,and 7, respectively.

[0016] This power detector is mounted on a dielectric substrate 11 of apower detecting device shown in FIG. 21.

[0017] This dielectric substrate 11 has a transmission line composed ofa central conductor 12 having a predetermined width and externalconductors 13A and 13B formed parallel with a predetermined spacingbetween them on the two sides of the central conductor 12.

[0018] The beam lead electrode 8 of this power detector 14 constructedas shown in FIG. 20 is connected to the central conductor 12 on thedielectric substrate 11.

[0019] The beam lead electrode 9 of the power detector 14 is connectedto ground (GND) which communicates with the external conductor 13B onthe dielectric substrate 11.

[0020] The beam lead electrode 10 of the power detector 14 is connectedto an output conductor 15 on the dielectric substrate 11.

[0021] The central conductor 12 on the dielectric substrate 11 isconnected to a connecting portion 17 via a coupling capacitor 16.

[0022] The output conductor 15 on the dielectric substrate 11 isconnected to ground (GND) which communicates with the external conductor13A via a bypass capacitor 18.

[0023] A lead line 19A for central conductor output is connected to theoutput conductor 15.

[0024] A lead line 19B for GND output is connected to the ground (GND)which communicates with the external conductor 13B.

[0025]FIG. 22 shows an equivalent circuit of this power detectingdevice.

[0026] That is, a signal S to be measured input from the connectingportion 17 is supplied to the two thermocouples 4A and 4B via thecoupling capacitor 16, and these two thermocouples 4A and 4B generateheat.

[0027] The electromotive forces generated in the two thermocouples 4Aand 4B by the heat generated by these two thermocouples 4A and 4B areadded and output from the lead lines 19A and 19B.

[0028] In the power detecting device constructed as above, theupper-limit value of a band in which the sensitivity lowers by 1 dBextends to 32 GHz.

[0029] In addition to the above system (so-called direct heating type),a so-called indirect heating system is also proposed as the thermocouplesystem. In this indirect heating system, a resistor for converting apower signal to be measured into heat, i.e., an input resistor, and athermocouple for detecting a temperature rise resulting from the heatgenerated by this resistor, are separated from each other.

[0030] This indirect heating type thermocouple has a longer responsetime than that of the direct heating type thermocouple. However, thenumber of thermocouples can be arbitrarily increased independently ofthe resistor, and a signal having magnitude directly proportional to thenumber of these thermocouples can be output.

[0031] Accordingly, this indirect heating type thermocouple has theadvantage that high detectivity is obtained. Thermocouples havingfrequency characteristics of about 20-odd GHz have been realized.

[0032] In the power detector and the power detecting device using thedirect heating type thermocouples described above, a signal is suppliedto the thermocouples themselves to cause these thermocouples to outputDC electromotive forces. Hence, the power of a DC signal cannot bedetected. Also, since the capacitance of a capacitor formable on asubstrate is limited, the power of a low-frequency signal cannot beaccurately detected.

[0033] Additionally, in the power detector and the power detectingdevice using the direct heating type thermocouples described above, thetwo thermocouples split the load on an input signal, and impedancematching is difficult owing to the influence of the capacitor.Therefore, it is difficult to further extend the upper-limit detectionfrequency.

[0034] Furthermore, in the power detector and the power detecting deviceusing the direct heating type thermocouples described above, a largernumber of thermocouples must be provided in the power detecting elementin order to detect micro watt power at high sensitivity.

[0035] Unfortunately, in the power detector and the power detectingdevice using the direct heating type thermocouples described above, ifthe number of thermocouples is increased, the number of necessarycapacitors increases accordingly. This makes impedance matching moredifficult. As a consequence, the frequency characteristic must besacrificed.

[0036] Especially in recent years, RF communication apparatuses usingmillimeter waves and microwaves are extensively developed.

[0037] To measure these communication apparatuses, it is increasinglydemanded to accurately detect the power of signals with higherfrequencies. However, the conventional power detecting elements andpower detecting devices described above cannot satisfactorily meet thisdemand.

[0038] Also, in the power detector and the power detecting device usingthe direct heating type thermocouples described above, electronicmaterials forming the input resistor and the thermocouple are different.This complicates the manufacturing method. Additionally, no knowledgefor effectively controlling the difference between the shape of theinput resistor electrode and the shape of the resistor has beenobtained.

[0039] That is, in the power detector and the power detecting deviceusing the direct heating type thermocouples, no knowledge about optimumwiring patterns for connecting the input resistor electrode to theresistor has been obtained. Consequently, the upper limit of measurablefrequencies is about 20-odd GHz as mentioned earlier.

DISCLOSURE OF INVENTION

[0040] The present invention has been made in consideration of the abovesituation, and has as its object to provide a wide-band RF signal powerdetecting element which is easy to manufacture, has a high upper-limitdetection frequency, can detect power from direct current, and has afrequency characteristic not influenced by the number of thermocouples.

[0041] It is another object of the present invention to provide a powerdetecting device using a wide-band RF power detecting element which iseasy to manufacture, has a high upper-limit detection frequency, candetect power from direct current, and has a frequency characteristic notinfluenced by the number of thermocouples.

[0042] According to one aspect of the present invention, there isprovided a wide-band RF signal power detecting element comprising

[0043] an insulating substrate,

[0044] a thin-film resistor formed on the substrate to absorb power of asignal to be measured and generate heat,

[0045] first and second ground electrodes formed by thin-filmconductors, adjacent to an edge of the substrate, and separated fromeach other,

[0046] a first thin-film connecting portion formed on the substrate toelectrically connect the first ground electrode to the thin-filmresistor,

[0047] a second thin-film connecting portion formed on the substrate toelectrically connect the second ground electrode to the thin-filmresistor, made to narrow a gap between the first and second thin-filmconnecting portions toward the thin-film resistor, and connected to thethin-film resistor with the thin-film resistor interposed between thefirst and second thin-film connecting portions, and

[0048] a thin-film thermocouple formed adjacent to and away from thethin-film resistor with a predetermined gap between them to detect atemperature rise of the thin-film resistor.

[0049] According to another aspect of the present invention, there isprovided a wide-band RF signal power detecting element comprising

[0050] an insulating substrate,

[0051] at least one thin-film resistor formed on the substrate to absorbpower of a signal to be measured and generate heat,

[0052] first and second ground electrodes formed by thin-filmconductors, adjacent to an edge of the substrate, and separated fromeach other,

[0053] a first thin-film connecting portion formed on the substrate toelectrically connect the first ground electrode to the at least onethin-film resistor,

[0054] a second thin-film connecting portion formed on the substrate toelectrically connect the second ground electrode to the at least onethin-film resistor, and made to narrow a gap between the first andsecond thin-film connecting portions toward the at least one thin-filmresistor,

[0055] an input electrode formed adjacent to the edge of the substrateand between the first and second ground electrodes,

[0056] an input connecting portion connected to the at least onethin-film resistor, with the at least one thin-film resistor interposedbetween the first and second thin-film connecting portions, toelectrically connect the input electrode to the at least one thin-filmresistor, such that a width of the input connecting portion decreasesfrom the input electrode toward the at least one thin-film resistor, andthat gaps between the input connecting portion and the first and secondthin-film connecting portions narrow toward the at least one thin-filmresistor, and

[0057] a thin-film thermocouple formed adjacent to and away from the atleast one thin-film resistor with a predetermined gap between them todetect a temperature rise of the at least one thin-film resistor.

[0058] According to still another aspect of the present invention, thereis provided a power detecting device comprising

[0059] a power detecting element comprising

[0060] an insulating substrate,

[0061] at least one thin-film resistor formed on the substrate to absorbpower of a signal to be measured and generate heat,

[0062] first and second ground electrodes formed by thin-filmconductors, adjacent to an edge of the substrate, and separated fromeach other,

[0063] a first thin-film connecting portion formed on the substrate toelectrically connect the first ground electrode to the at least onethin-film resistor,

[0064] a second thin-film connecting portion formed on the substrate toelectrically connect the second ground electrode to the at least onethin-film resistor, and made to narrow a gap between the first andsecond thin-film connecting portions toward the at least one thin-filmresistor,

[0065] an input electrode formed adjacent to the edge of the substrateand between the first and second ground electrodes,

[0066] an input connecting portion connected to the at least onethin-film resistor, with the at least one thin-film resistor interposedbetween the first and second thin-film connecting portions, toelectrically connect the input electrode to the at least one thin-filmresistor, such that a width of the input connecting portion decreasesfrom the input electrode toward the at least one thin-film resistor, andthat gaps between the input connecting portion and the first and secondthin-film connecting portions narrow toward the at least one thin-filmresistor, and

[0067] a thin-film thermocouple formed away from the at least onethin-film resistor with a predetermined gap between them to detect atemperature rise of the at least one thin-film resistor, and

[0068] a module substrate made larger than the substrate of thewide-band RF signal power detecting element, and comprising a centralconductor and a ground conductor formed by patterning on one surface ofthe module substrate to guide a signal to be measured, and mountportions formed, in one-to-one correspondence with the electrodes of thewide-band RF signal power detecting element, at a distal end of thecentral conductor and in a portion of the ground conductor in thevicinity of the distal end of the central conductor, the modulesubstrate fixing the wide-band RF signal power detecting element to theone surface with the electrodes of the power detecting element joined tothe mount portions, supplying a signal to be measured to between theelectrodes of the wide-band RF signal power detecting element, andoutputting a signal corresponding to power of the signal to be measured,

[0069] characterized in that transmission impedance between the centralconductor and the ground conductor of the module substrate is madesubstantially equal to transmission impedance between the electrodes ofthe wide-band RF signal power detecting element, and the centralconductor is given an inductance component corresponding to acapacitance component increased by junctions between the mount portionsand the electrodes of the wide-band RF signal power detecting element.

BRIEF DESCRIPTION OF DRAWINGS

[0070]FIG. 1 is a plan view showing a wide-band RF signal powerdetecting element according to the first embodiment of the presentinvention;

[0071]FIG. 2 is a side view showing the wide-band RF signal powerdetecting element according to the first embodiment of the presentinvention;

[0072]FIG. 3 is a sectional view taken along a line III-III in FIG. 2;

[0073]FIG. 4 is a sectional view taken along a line IV-IV in FIG. 1;

[0074]FIG. 5 is a sectional view taken along a line V-V in FIG. 1;

[0075]FIG. 6 is a sectional view taken along a line VI-VI in FIG. 1;

[0076]FIG. 7 is a sectional view taken along a line VII-VII in FIG. 1;

[0077]FIG. 8 is a sectional view taken along a line VIII-VIII in FIG. 1;

[0078]FIG. 9 is an equivalent circuit diagram of the wide-band RF signalpower detecting element according to the first embodiment of the presentinvention;

[0079]FIG. 10 is a schematic plan view showing a power detecting deviceusing the wide-band RF signal power detecting element according to thefirst embodiment of the present invention;

[0080]FIG. 11 is an enlarged view of the main components in FIG. 10;

[0081]FIG. 12 is a graph showing the frequency characteristics of thepower detecting device using wide-band RF signal power detecting elementaccording to the first embodiment of the present invention;

[0082]FIG. 13 is a graph showing the frequency characteristic of thepower detecting device using wide-band RF signal power detecting elementaccording to the first embodiment of the present invention;

[0083]FIG. 14 is a plan view showing a wide-band RF signal powerdetecting element according to the second embodiment of the presentinvention;

[0084]FIG. 15 is a side view showing the wide-band RF signal powerdetecting element according to the second embodiment of the presentinvention;

[0085]FIG. 16 is a sectional view taken along a line XVI-XVI in FIG. 15;

[0086]FIG. 17 is a sectional view taken along a line XVII-XVII in FIG.16;

[0087]FIG. 18 is a sectional view taken along a line XVIII-XVIII in FIG.16;

[0088]FIG. 19 is a plan view showing a wide-band RF signal powerdetecting element according to the third embodiment of the presentinvention;

[0089]FIG. 20 is a plan view showing a conventional power detectingelement;

[0090]FIG. 21 is a plan view showing a conventional power detectingdevice;

[0091]FIG. 22 is an equivalent circuit diagram of the conventional powerdetecting device;

[0092]FIG. 23A is a perspective view showing a module substrate 111 onwhich a wide-band RF signal power detecting element (power sensorelement) 110 according to the fourth embodiment of the present inventionis mounted;

[0093]FIG. 23B is a perspective view showing a coaxial type wide-band RFsignal power detecting device (coaxial power sensor) containing themodule substrate 111 according to the fourth embodiment of the presentinvention;

[0094]FIG. 24 is a plan view showing the structure of a waveguide typewide-band RF signal power detecting element (power sensor element)according to the fifth embodiment of the present invention;

[0095]FIGS. 25A and 25B are plan views showing the structures of finline module substrates 231 a and 231 b, respectively, used to match witha waveguide in the waveguide type wide-band RF signal power detectingdevice according to the fifth embodiment of the present invention;

[0096]FIGS. 26A and 26B are graphs showing the measurement results of anSWR in the waveguide type wide-band RF signal power detecting deviceaccording to the fifth embodiment of the present invention;

[0097]FIG. 27 is a perspective view showing the packaged state of thewaveguide type wide-band RF signal power detecting device according tothe fifth embodiment of the present invention;

[0098]FIG. 28A is a perspective view showing the packaged state of awaveguide type wide-band RF signal power detecting device (power sensor)according to the sixth embodiment of the present invention; and

[0099]FIG. 28B is an exploded perspective view showing the waveguidetype wide-band RF signal power detecting device (power sensor) accordingto the sixth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0100] First, an outline of the present invention will be describedbelow.

[0101] A wide-band RF signal power detecting element according to thepresent invention is based on the finding that the difference betweenthe shape of an electrode for an input resistor and the shape of theresistor in the indirect heating type thermocouple described previouslycan be coped with.

[0102] That is, a wide-band RF signal power detecting element accordingto the present invention is based on the finding that there are optimumwiring patterns for connecting the input resistor electrode to theresistor and the development of a means capable of greatly broadeningthe frequency characteristic.

[0103] Additionally, a power detecting device according to the presentinvention is based on the development of a method capable of correctingdeterioration of the frequency characteristic resulting from an increasein the capacitance produced between electrodes, when a wide-band RFsignal power detecting element according to the present invention ismounted on a coplanar module substrate.

[0104] Furthermore, in the conventional indirect heating type devices,electronic materials forming the input resistor and the thermocouple aredifferent. In contrast, a wide-band RF signal power detecting elementaccording to the present invention is based on the fact that a powerdetecting element having excellent characteristics can be realized evenwith the use of the same electronic material, i.e., is based on thedevelopment of a simple manufacturing method.

[0105] More specifically, a first wide-band RF signal power detectingelement according to the present invention comprises

[0106] an insulating substrate (21),

[0107] a thin-film resistor (22 a) formed on the substrate to absorbpower of a signal to be measured and generate heat,

[0108] an input electrode (26) formed by a thin-film metal at one end ofthe substrate,

[0109] a ground electrode (27, 28) formed by a thin-film metal at thesame end of the substrate,

[0110] a first connecting portion (23) for electrically connecting oneend of the thin-film resistor to the input electrode,

[0111] a second connecting portion (24, 25) for connecting the other endof the thin-film resistor to the ground electrode,

[0112] a thin-film thermocouple (30, 35) formed in the vicinity of thethin-film resistor to detect a temperature rise caused by heatgeneration by the thin-film resistor, and

[0113] an output electrode (38, 39) formed for the thin-filmthermocouple,

[0114] wherein transmission impedance between the input electrode andfirst connecting portion and the ground electrode and second connectingportion is held at a predetermined value.

[0115] A second wide-band RF signal power detecting element according tothe present invention is the first wide-band RF signal power detectingelement described above, wherein

[0116] the thin-film resistor is made smaller than the input electrodeand the ground electrode, and

[0117] the first connecting portion widens toward the input electrode.

[0118] A third wide-band RF signal power detecting element according tothe present invention is the first or second wide-band RF signal powerdetecting element described above, wherein

[0119] the ground electrode and the second connecting portion are soformed as to sandwich the input electrode and the first connectingportion.

[0120] A fourth wide-band RF signal power detecting element according tothe present invention comprises

[0121] an insulating substrate (21),

[0122] first and second thin-film resistors (20 a′, 20 a′) formed on thesubstrate to absorb power of a signal to be measured and generate heat,

[0123] an input electrode (26) formed by a thin-film metal at one end ofthe substrate,

[0124] a pair of ground electrodes (27, 28) formed by a thin-film metalto sandwich the input electrode at the same end of the substrate,

[0125] a first connecting portion (23) for electrically connecting oneend of each of the first and second thin-film resistors to the inputelectrode,

[0126] a second connecting portion (24) and a third connecting portion(25) for connecting the other ends of the first and second thin-filmresistors, respectively, to the pair of ground electrodes,

[0127] a thermocouple (30, 35) formed in the vicinity of the first andsecond thin-film resistors to detect a temperature rise caused by heatgeneration by the first and second thin-film resistors, and

[0128] an output electrode (38, 39) formed for the thermocouple,

[0129] wherein the first and second thin-film resistors are made smallerthan the input electrode and the ground electrodes,

[0130] the first connecting portion widens toward the input electrode,and

[0131] transmission impedance between the input electrode and firstconnecting portion and the pair of ground electrodes and second andthird connecting portions is held at a predetermined value.

[0132] A fifth wide-band RF signal power detecting element according tothe present invention comprises

[0133] an insulating substrate (21),

[0134] a thin-film resistor (22 a) formed on one surface of thesubstrate to absorb power of a signal to be measured and generate heat,

[0135] an input electrode (26) formed by a thin-film metal at one end onone surface of the substrate,

[0136] a pair of ground electrodes (26, 27) formed by a thin-film metalto sandwich the input electrode at the same end on the same surface ofthe substrate,

[0137] a first connecting portion formed (23) by a thin-film metal toelectrically connect one end of the thin-film resistor to the inputelectrode on the same surface of the substrate,

[0138] a second connecting portion (24) and a third connecting portion(25) formed by a thin-film metal to electrically connect the other endof the thin-film resistor to the pair of ground electrodes on the samesurface of the substrate,

[0139] a thermocouple (30, 35) comprising a first thin-film portionformed on a side away from the thin-film resistor with the secondconnecting portion between them on the same surface of the substrate,and a second thin-film portion made of an electronic material differentfrom the first thin-film portion and connected to the first thin-filmportion in a position close to the thin-film resistor, the thermocouplegenerating a signal corresponding to a temperature rise caused by heatgeneration by the thin-film resistor, and

[0140] an output electrode (38, 39) for outputting the signal generatedby the thermocouple,

[0141] wherein the first connecting portion is widened from one end ofthe thin-film resistor toward the input electrode, and

[0142] a ratio of a width of the input electrode and the firstconnecting portion to a gap between the ground electrode and the secondconnecting portion is held substantially constant, thereby holdingtransmission impedance between the input electrode and first connectingportion and the ground electrode and second and third connectingportions at a predetermined value.

[0143] A sixth wide-band RF signal power detecting element according tothe present invention is any one of the first to fifth wide-band RFsignal power detecting elements described above, wherein the thin-filmresistor and one thin-film portion of the thermocouple are made of amicro-crystalline silicon germanium thin film.

[0144] A seventh wide-band RF signal power detecting element accordingto the present invention is any one of the first to sixth wide-band RFsignal power detecting elements described above, wherein a plurality ofsubstantially fan-shaped thermocouples are radially arranged around thethin-film resistor on one surface of the substrate, and the plurality ofthermocouples are connected in series.

[0145] A first wide-band RF signal power detecting device according tothe present invention comprises

[0146] a power detecting element (20) comprising a substrate, a resistorformed on the substrate, electrodes formed on one surface of thesubstrate and connected to two ends of the resistor, and a thermocouplefor outputting a signal corresponding to heat generated by the resistor,and set such that transmission impedance between the electrodes has apredetermined value, and

[0147] a module substrate (43) made larger than the substrate of thewide-band RF signal power detecting element, and comprising a centralconductor and a ground conductor formed by patterning on one surface ofthe module substrate to guide a signal to be measured, and mountportions formed, in one-to-one correspondence with the electrodes of thewide-band RF signal power detecting element, at a distal end of thecentral conductor and in a portion of the ground conductor in thevicinity of the distal end of the central conductor, the modulesubstrate fixing the wide-band RF signal power detecting element to theone surface with the electrodes of the power detecting element joined tothe mount portions, supplying a signal to be measured to between theelectrodes of the power detecting element, and outputting a signalcorresponding to power of the signal to be measured,

[0148] wherein transmission impedance between the central conductor andthe ground conductor of the module substrate is made substantially equalto transmission impedance between the electrodes of the wide-band RFsignal power detecting element, and the central conductor is given aninductance component corresponding to a capacitance component increasedby junctions between the mount portions and the electrodes of thewide-band RF signal power detecting element.

[0149] A second wide-band RF signal power detecting device according tothe present invention is the first wide-band RF signal power detectingdevice described above, wherein the inductance component correspondingto the increased capacitance component is formed in the vicinity of themount portion of the central conductor.

[0150] Each embodiment of the present invention based on theaforementioned outline will be described below with reference to theaccompanying drawings.

[0151] (First Embodiment)

[0152] A power detecting element 20 according to the first embodiment ofthe present invention will be described below with reference to FIGS. 1to 8.

[0153] As shown in FIG. 1, this power detecting element 20 is formed ona rectangular insulating sapphire substrate 21 about 1 mm in side lengthand about 20 μm (micrometers) thick.

[0154] In this embodiment, a sapphire substrate having small dielectricloss and high thermal conductivity is used as the insulating substrate21. However, it is also possible to use, e.g., glass, fused quartz, andalumina, in addition to sapphire.

[0155] As shown in FIG. 3, a thin-film member 22 made frommicro-crystalline silicon germanium is formed from the center of onesurface 21 a of the substrate 21 to a side 21 b.

[0156] This thin-film member 22 has a thickness of approximately 1 μmand is composed of a resistor 22 a and first, second, and thirdextending portions 22 b, 22 c, and 22 d. The first extending portion 22b runs from one end of the resistor 22 a to the center of the side 21 bof the substrate 21. The second extending portion 22 c runs from theother end of the resistor 22 a to the corner between the side 21 b and aside 21 c of the substrate 21. The third extending portion 22 d connectswith the second extending portion 22 c and runs from the other end ofthe resistor 22 a to the corner between the side 21 b and a side 21 d ofthe substrate 21.

[0157] The first extending portion 22 b is axially symmetrical with aline connecting the center of the substrate 21 to the center of the side21 b. Also, a width Wa of this first extending portion 22 b in adirection along the side 21 b of the substrate 21 monotonicallyincreases in a direction from one end of the resistor 22 a to the side21 b of the substrate 21.

[0158] A width Wb of the second and third extending portions 22 c and 22d in the direction along the side 21 b of the substrate 21 and adistance Ga from these second and third extending portions 22 c and 22 dto the first extending portion 22 b increase in direct proportion to thewidth Wa of the first extending portion 22 b.

[0159] As shown in FIG. 4, an input connecting portion 23 having thesame external shape as the first extending portion 22 b and made of athin-film metal is formed to overlap the first extending portion 22 b.

[0160] Also, as shown in FIG. 1, ground (GND) connecting portions 24 and25 having the same external shapes as the second and third extendingportions 22 c and 22 d, respectively, and made of a thin-film metal areformed to overlap the second and third extending portions 22 c and 22 d,respectively.

[0161] These ground connecting portions 24 and 25 communicate with eachother at the other end of the resistor 22 a.

[0162] These connecting portions 23, 24, and 25 are made of alow-resistance metal film (or a plurality of stacked layers of thinfilms of different metals) of, e.g., platinum or gold, having athickness of about 0.5 μm.

[0163] An input electrode 26 and ground (GND) electrodes 27 and 28, eachhaving a wide rectangular shape, are formed on end portions 23 a, 24 a,and 25 a of the connecting portions 23, 24, and 25, respectively, on theside 21 b of the substrate 21.

[0164] These electrodes 26, 27, and 28 are made of a gold-plated layerabout 5 μm thick.

[0165] The electrodes 26, 27, and 28 are connected to the two ends ofthe resistor 22 a via the connecting portions 23, 24, and 25,respectively.

[0166] The resistance of the resistor 22 c, which forms a thin-filmresistor by connecting its two ends to the input connecting portion 23and the ground connecting portions 24 and 25, is determined by thematerial of the thin-film member 22 and the width, length, and thicknessof the resistor 22 a.

[0167] In this embodiment, the area of the resistor 22 a is decreased sothat heat generating portions of the power detecting element 20 areconcentrated into one point in the center of the substrate 21, and thatthe resistor 22 a is a pure resistor up to a RF region. Also, thedimensions of individual portions are so set that the resistance is 50Ω(or 75Ω) which is equal to the transmission impedance of a RF coaxialcable.

[0168] In contrast to this small resistor 22 a, the input electrode 26and the ground electrodes 27 and 28 are so formed as to have large areasin order to ensure the easiness of packaging.

[0169] The connecting portions 23, 24, and 25 connecting with the inputelectrode 26 and the ground electrodes 27 and 28 widen toward the side21 b of the substrate 21 and communicate with the electrodes 26, 27, and28.

[0170] Additionally, to form a coplanar transmission line from the inputelectrode 26 and the ground electrodes 27 and 28 to the two ends of theresistor 22 c, the ratio of the width Wa of the input connecting portion23 and the input electrode 26 to the gap Ga between the groundconnecting portions 24 and 25 and the ground electrodes 27 and 28 isheld substantially constant. Consequently, the impedance viewed from theinput terminal is substantially equal to the resistance of the resistor22 a.

[0171] Note that letting W be the width of a central conductor and G bethe gap between the central conductor and a ground conductor, thetransmission impedance of a coplanar transmission line is determinedsubstantially in accordance with the value of (W+G)/W and the linelength.

[0172] Theoretically, as in the case of a module substrate 43 to bedescribed later, it is necessary to nonlinearly change the width of thecentral conductor in accordance with the length of the transmissionline.

[0173] In this power detecting element 20, however, the transmissionline length is short. Therefore, the width of the input connectingportion 23 and the gap between the ground connecting portions 24 and 25are linearly increased, and the ratio of the width Wa to the gap Ga isfixed.

[0174] With the above arrangement, the frequency characteristic of thispower detecting element 20 broadens to 65 GHz or more, which is twicethe aforesaid conventional frequency or more.

[0175] Two thermocouples 30 and 35 are formed on a side 21 e of thesubstrate 21 away from the resistor 22 a with the ground connectingportions 24 and 25 between them.

[0176] The thermocouple 30 has a thin-film member 31 formed into asubstantially rectangular shape long from end to end on one surface 21 aof the substrate 21.

[0177] The thermocouple 35 has a thin-film member 36 formed into asubstantially rectangular shape long from side to side on one surface 21a of the substrate 21.

[0178] These thin-film members 31 and 36 are made of a micro-crystallinesilicon germanium thin film having the same thickness as the thin-filmmember 22 forming the resistor 22 a.

[0179] As shown in FIG. 3, corners 31 a and 36 a of the thin-filmmembers 31 and 36 are close to the resistor 22 a, and diagonal corners31 b and 36 b are far from the resistor 22 a.

[0180] As shown in FIG. 1, one end 32 a of a first output connectingportion 32 is connected to overlap the corner 31 a of the thin-filmmember 31.

[0181] This connecting portion is a hot junction of the thermocouple 30.

[0182] The first output connecting portion 32 so runs as to surround theperimeter of the thin-film member 31.

[0183] The other end 32 b of this first output connecting portion 32forms a cold junction of the thermocouple 30 and runs to the cornerbetween the two sides 21 c and 21 e of the substrate 21.

[0184] One end 33 a of an intermediate connecting portion 33 isconnected to overlap the corner 31 b of the thin-film member 31 in widearea.

[0185] This connecting portion forms a cold junction of thethermocouples 30 and 35.

[0186] The other end 33 b of the intermediate connecting portion 33 isconnected to overlap the corner 36 a of the thin-film member 36.

[0187] This connecting portion forms a hot junction of the thermocouple35.

[0188] A second output connecting portion 37 serving as a cold junctionof the thermocouple 36 is connected to overlap the corner 36 b of thethin-film member 36.

[0189] The first and second output connecting portions 32 and 37 and theintermediate connecting portion 33 are made of a low-resistance metalthin film, similar to the input connecting portion 23 and the groundconnecting portions 24 and 25.

[0190] On the surfaces of the first and second output connectingportions 32 and 37 close to the side 21 e of the substrate 21, outputelectrodes 38 and 39 having a rectangular shape long from end to end andmade of a gold-plated layer about 5 μm thick are formed at the samelevel as the input electrode 26 and the ground electrodes 27 and 28.

[0191] Between the other end 32 b of the first output connecting portion32 and the upper surface of the substrate 21, a thin-film member 34 madefrom micro-crystalline silicon germanium is formed into a rectangularshape long from end to end, in order to level the surface of the end 32b of the first output connecting portion 32 with the surface of thesecond output connecting portion 37. In the power detecting element 20constructed as above, as shown in an equivalent circuit diagram of FIG.9, when a signal S to be measured is supplied to the input electrode 26and the ground electrodes 27 and 28 connected to the two ends of theresistor 22 b, the resistor 22 b generates heat in accordance with thepower of the signal S.

[0192] This heat raises the temperature at a hot junction Hj of the twothermocouples 30 and 35. Consequently, these two thermocouples 30 and 35generate electromotive forces V directly proportional to a temperaturedifference ΔT between the hot junction Hj and a cold junction Cj.

[0193] An output of 2 V obtained by adding the electromotive forces V ofthe two thermocouples 30 and 35 is output from the output terminals 38and 39.

[0194] Note that the micro-crystalline silicon germanium forming thethin-film members 22, 31, 34, and 36 has a Seebeck coefficient, whichrepresents the magnitude of electromotive force corresponding to thetemperature difference between a hot junction and a cold junction, of100 to 200 μV/K.

[0195] This value is about an order of magnitude larger than those ofconventional metal thin-film materials.

[0196] In addition, the micro-crystalline silicon germanium forming thethin-film members 22, 31, 34, and 36 has dependence of conductivity ontemperature far smaller than those of other micro-crystallinesemiconductor thin films. Therefore, as described above, thismicro-crystalline silicon germanium can be used as the resistor 22 a forconverting a signal into heat and as one thermocouple material of eachof the two thermocouples 30 and 35.

[0197] Furthermore, the micro-crystalline silicon germanium is stable ata high temperature of 600° C. and hence is immune to burning out evenwhen large power to be measured is supplied to the resistor 22 a.

[0198] Steps of manufacturing this power detecting element 20 are asdescribed in (a) to (d) below.

[0199] (a) A sapphire substrate (or a glass substrate, a fused quartzsubstrate, or the like) having a size by which a plurality of powerdetecting elements 20 can be formed is cleaned. After that, amicro-crystalline silicon germanium thin film is deposited on one entiresurface of this substrate by plasma CVD (Chemical Vapor Deposition).

[0200] (b) Thin-film members 22, 31, 34, and 36 corresponding to aplurality of elements are formed by patterning by using photoetching.

[0201] (c) A thin metal film is deposited on these thin-film members 22,31, 34, and 36 by using vacuum vapor deposition or sputtering. Afterthat, connecting portions corresponding to a plurality of elements areformed by using photoetching.

[0202] (d) A gold-plated layer is formed on these connecting portions toform electrodes, and the power detecting elements 20 are cut out by adicer or the like.

[0203] In the first embodiment of the present invention as describedabove, the resistor 22 a and one thermocouple material of eachthermocouple are formed by the same micro-crystalline silicon germaniumthin film. Additionally, the connecting portions and electrodes formedon this micro-crystalline silicon germanium thin film are formed by thesame metal thin film, resulting in simple manufacturing steps.Accordingly, it is possible to inexpensively manufacture the powerdetecting elements 20 for wide-band RF signals, which have high yieldand uniform characteristics.

[0204] The power detecting element 20 manufactured in this way isincorporated, as it is mounted on a module substrate 43, into a case 41of a power detecting device 40, as shown in FIG. 10.

[0205] This case 41 is made of a metal in order to thermally shield theexterior and the interior, and is formed into, e.g., a cylindricalshape. A coaxial connector 42 for connecting a coaxial cable (not shown)is formed in one end of this case 41.

[0206] The module substrate 43 guides a signal to be measured input fromthe coaxial connector 42 to the power detecting element 20 andexternally outputs an output signal from the power detecting element 20.

[0207] This module substrate 43 has the shape of a rectangle. A centralconductor 44 is formed by patterning from an end 43 b to an end 43 c ofa surface 43 a of the module substrate 43.

[0208] This central conductor 44 connects a core 42 a of the coaxialconnector 42 to the input electrode 26 of the power detecting element20.

[0209] That is, the central conductor 44 is so formed as to decrease itsthickness in a direction from the end 43 b to the end 43 c of the modulesubstrate 43.

[0210] As shown in FIG. 11, a mount portion 44 a having a width Wb and alength Lb, substantially equal to those of the input electrode 26 of thepower detecting element 20, is formed at the end portion of the centralconductor 44.

[0211] This mount portion 44 a has an elongated portion 44 b which iselongated, with the same width Wb, by a predetermined distance Lc towardone end 40 b of the module substrate 43.

[0212] Ground (GND) conductors 45 and 46 are formed on the two sides ofthe central conductor 44 by patterning.

[0213] These ground conductors 45 and 46 form a coplanar transmissionline together with the central conductor 44. To be equal to thetransmission impedance (the resistance of the resistor 22 a of the powerdetecting element 20) of the coaxial cable, the ratio of a width Wc ofthe central conductor 44 to a gap Gc from the central conductor 44 tothe ground conductors 45 and 46 is held substantially constant.

[0214] These portions of the ground conductors 45 and 46 that are on thetwo sides of the mount portion 44 a of the central conductor 44 haverectangular mount portions 45 a and 46 a, respectively, matching theground (GND) electrodes 27 and 28 of the power detecting elements 20.

[0215] These ground conductors 45 and 46 connect with each other in therear portion of the module substrate 43 and are in contact with the case41 in two side portions 43 d and 43 e of the module substrate 43.

[0216] The elongated portion 44 b of the central conductor 44 preventsdisturbance of the impedance, caused by an increase in the capacitancebetween the junction portion of the input electrode 26 of the powerdetecting element 20 and the mount portion 44 a and the junctionportions of the ground electrodes 27 and 28 of the power detectingelement 20 and the mount portions 45 a and 46 a, when the powerdetecting element 20 is mounted on the module substrate 43.

[0217] That is, the ratio of the width Wc of the central conductor 44 tothe gap Gc between the central conductor 44 and the ground conductors 45and 46 is changed (made smaller than the width determined by the ratio)only in this portion. This gives the central conductor 44 inductancecorresponding to the capacitance increase, thereby preventingdisturbance to the impedance resulting from the capacitance increase.

[0218] In a central portion of the module substrate 43, a pair of outputconductors 47 and 48 are formed parallel by patterning.

[0219] The spacing and width of these output conductors 47 and 48 aresubstantially equal to the spacing and width of the output electrodes 38and 39 of the power detecting element 20.

[0220] The power detecting element 20 is soldered to the modulesubstrate 43 constructed as above, with the surface 21 a of thesubstrate 21 facing the surface 43 a of the module substrate 43, theinput electrode 26 and the ground electrodes 27 and 28 overlapping themount portions 44 a, 45 a, and 46 a of the module substrate 43, and theoutput electrodes 38 and 39 overlapping the output conductors 47 and 48.

[0221] Although not shown, an amplifier (e.g., a chopper amplifier) foramplifying output signals from the output conductors 47 and 48 is formedat the end 43 c of the module substrate 43.

[0222] That is, a series output of the electromotive forces of the twothermocouples is amplified by this amplifier and output to the outsideof the case 41. An indicator or the like indicates the power of thissignal.

[0223]FIG. 12 shows the measurement results of the frequency vs.sensitivity characteristics of this power detecting device 40 and theconventional device described previously.

[0224] A curve A in FIG. 12 indicates the characteristic of the powerdetecting device 40 with reference to the output when direct current isinput.

[0225] A curve B in FIG. 12 indicates the characteristic of theconventional device.

[0226] It is evident from FIG. 12 that in the conventional device theupper limit of the frequency range within which the sensitivity lowersby 1 dB is 32 GHz, whereas the frequency range of the power detectingdevice 40 of this embodiment widens from DC to 65 GHz, i.e., has acharacteristic twice as broad as that of the conventional device ormore.

[0227] A curve C in FIG. 12 indicates the characteristic when thecentral conductor 44 of the module substrate 43 has no elongated portion44 b.

[0228] If this is the case, the sensitivity lowers by 1 dB atsubstantially 40 GHz.

[0229] This demonstrates that the characteristics of the power detectingelement 20 can be well brought out by the formation of this elongatedportion 44 b.

[0230]FIG. 13 shows the measurement result of the frequency-to-voltagestanding wave ratio of the power detecting device 40.

[0231] The characteristic shown in FIG. 13 is in good agreement with thecharacteristic A shown in FIG. 12.

[0232] Accordingly, these characteristics show that the SWR (StandingWave Ratio) of the power detecting device 40 of this embodiment isdecreased to 1.5 or less from DC to 65 GHz, so this power detectingdevice 40 can accurately detect power, over this wide band, withoutbeing largely influenced by reflecting waves.

[0233] (Second Embodiment)

[0234] In the above first embodiment, one thin-film resistor-absorbs thepower of a signal to be measured. However, a plurality of thin-filmtransistors can also absorb the power of a signal to be measured.

[0235] For example, as the second embodiment, a power detecting element20′ shown in FIG. 14 has two thin-film transistors 22 a′ and 22 a′ on asubstrate 21.

[0236] One end of each of these two thin-film transistors 22 a′ and 22a′ is connected to an input connecting portion 23.

[0237] The other end of one thin-film transistor 22 a′ is connected tothe distal end of a ground connecting portion 24.

[0238] The other end of the other thin-film resistor 22 a′ is connectedto the distal end of a ground connecting portion 25.

[0239] In this structure, by setting the resistance of each thin-filmresistor 22 a′ to be substantially twice that of the resistor 22 a inthe first embodiment, this resistance can be matched with thetransmission impedance viewed from an input electrode 26 and groundelectrodes 27 and 28.

[0240] The ends of the ground connecting portions can also be connectedto each other on the substrate 21.

[0241] The number of thin-film resistors is not limited to two and canbe further increased.

[0242] Since a plurality of thin-film resistors are formed as describedabove, the power of a signal to be measured is divisionally absorbed bythese resistors. This disperses the heat generation, increases theburnout level of each resistor, and improves the heat resistance.

[0243] Note that input resistors are separated from thermocouples, sothe pattern of these input resistors can be formed independently of thethermocouples. Accordingly, even if the number of thin-film transistorsis increased, the frequency characteristic does not deteriorate.

[0244] (Third Embodiment)

[0245] The power detecting element 20 of the first embodiment has twothermocouples. However, only one thermocouple can also be used if thesensitivity is of no great importance.

[0246] If, however, the sensitivity is of great importance, thesensitivity of the power detecting element 20 of the first embodimentcan be further increased by using three thermocouples.

[0247] FIGS. 15 to 19 show a power detecting element 50 having seventhermocouples according to this third embodiment.

[0248] In this power detecting element 50, as shown in FIG. 17, on onesurface 51 a of an insulating rectangular substrate 51, a resistor 52 aand first, second, and third extending portions 52 b, 52 c, and 52 d areformed by a thin-film member 52 made from micro-crystalline silicongermanium.

[0249] An input connecting portion 53 is formed to overlap the firstextending portion 52 b.

[0250] Ground (GND) connecting portions 54 and 55 are formed to overlapthe second and third extending portions 52 c and 52 d, respectively.

[0251] The input connecting portion 53 is so formed as to widen toward aside 51 b of the substrate 51. An input electrode 56 made of agold-plated layer is formed in an end portion 53 a of this inputconnecting portion 53.

[0252] The ground connecting portions 54 and 55 communicate with eachother at the other end of the resistor 52 a. These ground connectingportions 54 and 55 run to the corner between the side 51 b and a side 51c of the substrate 51 and to the corner between the side 51 b and a side51 d, respectively.

[0253] Ground electrodes 57 and 58 made of a gold-plated layer areformed in end portions 54 a and 55 a of the ground connecting portions54 and 55, respectively.

[0254] As in the power detecting element 20 of the first embodiment, theinput connecting portion 53 and the input electrode 56, and the groundconnecting portions 54 and 55 and the ground electrodes 57 and 58, areformed so that the ratio of the width of the input connecting portion 53and the input electrode 56 to the gap between the ground connectingportions 54 and 55 and the ground electrodes 57 and 58 is heldsubstantially constant, and so as to form a coplanar transmission linehaving transmission impedance substantially equal to the resistance ofthe resistor 52 a.

[0255] On the surface of the substrate 51 away from the groundconnecting portions 54 and 55 with the resistor 52 a between them, seventhermocouples 61 to 67 radially arrayed as shown in FIG. 15 are formed.

[0256] As shown in FIG. 17, these thermocouples 61 to 67 havesubstantially fan-shaped thin-film members 71 to 77, respectively, whichdivide the range from the ground connecting portions 54 and 55 to a side51 e of the substrate 51 into seven segments.

[0257] These thin-film members 71 to 77 are made from micro-crystallinesilicon germanium. As shown in FIG. 18, on the surfaces of thesethin-film members 71 to 77, insulating films 81 to 87 are formed exceptfor distal end portions 71 a to 77 a close to the resistor 52 a andouter edge portions 71 b to 77 b outside a circle of a predeterminedradius centering around the resistor 52 a.

[0258] A thin-film member 78 for receiving one output electrode isformed between the perimeter of the thin-film member 71 adjacent to theground connecting portion 54 and the corner between the two sides 51 cand 51 e of the substrate 51.

[0259] A thin-film member 79 for receiving the other output electroderuns between the outer edge of the thin-film member 77 adjacent to theground connecting portion 55 and the corner between the two sides 51 dand 51 e of the substrate 51.

[0260] Insulating films 88 a to 88 c are formed between intermediateportions, between the input connecting portion 53 and the groundconnecting portions 54 and 55, and the thin-film member 52.

[0261] One end 91 a of an output connecting portion 91 is connected tothe distal end portion 71 a of the thin-film member 71, adjacent to theground connecting portion 54, so as to overlap this end portion 71 a.

[0262] This connecting portion forms a hot junction of the thermocouple61.

[0263] The output connecting portion 91 extends from the distal endportion 71 a of the thin-film member 71 to the corner between the twosides 51 c and 51 e of the substrate 51, over the insulating film 81, soas to overlap the thin-film member 78.

[0264] One end 92 a of an intermediate connecting portion 92 isconnected to overlap the outer edge portion 71 b of the thin-film member71 in wide area.

[0265] This intermediate connecting portion 92 runs from the outer edgeportion 71 b of the thin-film member 71 to the distal end portion 72 aof the thin-film member 72, over the insulating film 81 and theinsulating film 82 of the adjacent thin-film member 72. The other end 92b of the intermediate connecting portion 92 is connected to the distalend portion 72 a of the thin-film member 72.

[0266] In a similar fashion, portions between the thin-film members 72to 77 are connected via intermediate connecting portions 93 to 97,respectively.

[0267] The outer edge portion 77 b of the thin-film member 77 isconnected to an output connecting portion 98 so formed as to overlap thethin-film member 79.

[0268] Output electrodes 99 and 100 made of a gold-plated layer areformed at the same level in the end portions of the output connectingportions 91 and 97.

[0269] In the power detecting element 50 constructed as above, the sumof the electromotive forces of the seven thermocouples 61 to 67 isoutput between the output electrodes 99 and 100.

[0270] In this power detecting element 50, as described above, the inputelectrode 56, the ground electrodes 57 and 58, and the resistor 52 a areconnected by the coplanar transmission line so that the transmissionimpedance is substantially equal to the resistance of the resistor 52 a.

[0271] Accordingly, this power detecting element 50 has a frequencycharacteristic exceeding 65 GHz, like the power detecting element 20 ofthe first embodiment.

[0272] In a power detecting device in which this power detecting element50 is mounted on a module substrate 43 described previously, therefore,electromotive force larger than that of the power detecting device 40 ofthe first embodiment can be obtained. This makes detection of micro wattpower possible.

[0273] In the above embodiment, the input connecting portion and theground connecting portions overlap in a broad range of the thin-filmmember forming the resistor. However, it is also possible to form athin-film member as a resistor only in a limited range on one surface ofa substrate and form connecting portions so that their end portionsoverlap the two ends of this resistor, thereby connecting theseconnecting portions to an input electrode and ground electrodes.

[0274] Also, in the module substrate 43 in the above embodiment, tocancel any capacitance increase caused by junctions between input andground electrodes of a power detecting element 20 and the mountportions, an elongated portion 44 b narrower than a predetermined widthdetermined by the transmission impedance is formed to connect with themount portion of a central conductor 44, thereby increasing theinductance in accordance with the capacitance increase.

[0275] The present invention, however, is not limited to thisembodiment. For example, the inductance corresponding to the capacitanceincrease can also be formed in a position separated from the mountportion of the central conductor 44.

[0276] Furthermore, while the width of the central conductor 44 is set,over its whole length, to a predetermined width determined by thetransmission impedance, a notch or the like is formed in a groundconductor 45 so as to partially widen the gap between the centralconductor 44 and the ground conductor 45. In this manner, the centralconductor 44 can be given an inductance corresponding to the capacitanceincrease caused by mounting of the power detecting element.

[0277] (Fourth Embodiment)

[0278]FIGS. 23A and 23B show a coaxial type wide-band RF signal powerdetecting device (coaxial power sensor) according to the fourthembodiment of the present invention.

[0279] That is, a module substrate 111 on which, as shown in FIG. 23A, awide-band RF signal power detecting element (power sensor element) 110,formed in the same manner as in the first to third embodiments describedabove, is mounted is incorporated, as shown in FIG. 23B, into a coaxialmodule tube 114 as a coaxial case, thereby realizing a coaxial typewide-band RF signal power detecting device (coaxial power sensor) 113.

[0280] Reference numeral 112 in FIG. 23A denotes solder for cementingused to mount the power detecting element (power sensor element) 110 onthe module substrate 111.

[0281] Reference numeral 115 in FIG. 23B denotes a contact portion thatprojects into the front end portion of the coaxial module tube 114 as acoaxial case incorporating the module substrate 111.

[0282] Reference numeral 116 in FIG. 23B denotes a hollow portion(absorber) of the coaxial module tube 114 as a coaxial caseincorporating the module substrate 111.

[0283] Reference numeral 117 in FIG. 23B denotes a lead line thatprojects from the rear end portion of the coaxial module tube 114 as acoaxial case incorporating the module substrate 111.

[0284] Reference numeral 118 in FIG. 23B denotes a cover attached to thecoaxial module tube 114 as a coaxial case incorporating the modulesubstrate 111.

[0285] That is, as shown in FIGS. 23A and 23B, this coaxial power sensor113 comprises the coaxial module tube 114 which transmits a RF signalsupplied, via a coaxial cable (not shown), from a RF signal source tothe contact portion 115, which projects into the front end portion ofthe coaxial module tube 114, of the module substrate 111, the modulesubstrate 111 formed inside this coaxial module tube 114, and the powersensor element 110 formed on this module substrate 111.

[0286] In this construction, a RF signal to be measured supplied fromthe coaxial cable (not shown) is transmitted to the module substrate 111via the contact portion 115 for matching conversion to a microstrip lineof a coplanar structure.

[0287] In this module substrate 111, the RF signal to be measured isconverted from a coaxial-mode electromagnetic wave, propagating in thecoaxial cable, into a coplanar-mode electromagnetic wave.

[0288] The coplanar-mode RF signal thus converted propagates in thevicinity of the surface of a dielectric material sandwiched between asignal line of a central conductor, as a microstrip line, on the modulesubstrate 111 and an external ground conductor. After that, this RFsignal is absorbed by the resistor of the power sensor element 110mounted on the module substrate 111 and thereby converted into heat.

[0289] The magnitude of the generation of heat by this conversion isdirectly proportional to the magnitude of the power of the supplied RFsignal to be measured.

[0290] The magnitude of the heat generation is converted into DC voltageby using a thermocouple placed close to the resistor of the power sensorelement 110.

[0291] This DC voltage is supplied to a dedicated meter (not shown) viathe lead line 117, and the magnitude of the voltage is displayed.

[0292] The contact portion 115 is formed on a surface in the center ofthe module substrate 111 and perpendicular to the longitudinal directionof the module substrate 111.

[0293] This contact portion 115 is desirably made of a thin-film piece,which has high electrical conductivity and is soft, such as a goldribbon, in order to improve the contact with a coaxial cable terminal(not shown).

[0294] Also, the material of the coaxial module tube 114 is desirably,e.g., copper or brass, having high electrical conductivity.

[0295] To decrease the cost of the coaxial module tube 114, it is alsoeffective to use plastic having a small linear expansion coefficient asa base material and to cover the surface with plating of anelectrically, thermally conductive material, such as gold or nickel.

[0296] As the coplanar module substrate 111, sapphire or aluminum havinga large dielectric constant and a small dielectric loss is used.

[0297] As a method of mounting the power sensor element 110 on thismodule substrate 111, a solder fusing method which uses the solder 112to mount the power detecting element (power sensor element) 110 on themodule substrate 111 as described earlier is used.

[0298] To absorb electromagnetic waves leaking outside the surface ofthe module substrate 111, the hollow portion 116 of the coaxial moduletube 114 is desirably filled with an electromagnetic wave absorber, suchas polyiron, in order to increase the measurement accuracy.

[0299] (Fifth Embodiment)

[0300] FIGS. 24 to 27 show a waveguide type wide-band RF signal powerdetecting element (power sensor element) and a waveguide type wide-bandRF signal power detecting apparatus using the element.

[0301] Coaxial type and waveguide type elements are possible asmillimeter-wave power sensor elements.

[0302] Of these elements, a coaxial type power detecting element (powersensor element) and a coaxial type power detecting device using the sameis realized in each of the first to fourth embodiments described above.

[0303] A waveguide type power detecting element (power sensor element)and a waveguide type power detecting device using the same can berealized by this fifth embodiment.

[0304] As shown in FIG. 24, the structure of a waveguide type powerdetecting element (power sensor element) is basically the same as thecoaxial type element except that the waveguide type element has twoinput terminals.

[0305] This results from the structure of fin line module substrates 231a and 231 b used to match with a waveguide as shown in FIGS. 25A and25B.

[0306] The common feature of the coaxial type and waveguide typeelements is that impedance mismatching is compensated for by using ageometrical shape, thereby obtaining desired performance (FIGS. 25A and25B).

[0307]FIG. 24 relates to the structure of a waveguide type powerdetecting element (power sensor element) 210 and is particularly a planview showing an element chip.

[0308] The chip size of this element is 0.9 mm square.

[0309] In this waveguide type power detecting element (power sensorelement) 210, a resistor 212 is formed in substantially the center of a75-μm thick glass substrate 211, and thermocouples 213 are formed tosurround this resistor 212, by using thin film deposition andlithography.

[0310] These thermocouples 213 include seven thermocouples 213 a to 213g formed in the same manner as the seven thermocouples 61 to 67 of thepower detecting element 50 according to the third embodiment shown inFIGS. 15 to 19.

[0311] This waveguide type power detecting element (power sensorelement) 210 has tapered electrodes 214 and 215 to suppress reflectionof incident millimeter-wave power.

[0312] The entrance opening of each taper is 0.4 mm, and its exitopening (facing the resistor 212) is 0.03 mm.

[0313] Accordingly, although the tapered electrodes 214 and 215 areformed to suppress reflection of incident millimeter-wave power, inpractice a large impedance change is readily produced by this abrupttaper. In effect, large reflection having a reflectance of 0.13 takesplace.

[0314] Meanwhile, to suppress reflection of incident waves to theresistor 212, the incident portion of this resistor 212 has apredetermined inclination angle (20 to 90°, desirably, 45 to 90°) to theaxial line. However, reflection having a reflectance of about 0.2 stilloccurs.

[0315] To decrease the reflectances (RF1) of both the tapered electrodes214 and 215 and the resistor 212, it is in principle possible toincrease the length of the tapered portion or decrease the inclinationangle of the resistor.

[0316] Unfortunately, neither method can be employed in the manufactureof an actual element for reasons, such as an increase in the responsetime, a reduction in the detectivity, and the difficulty of packaging ofthe element.

[0317] This is a barrier in developing millimeter-wave power sensors bythe conventional method.

[0318] This embodiment, therefore, as will be described later, ischaracterized in that the abovementioned two reflectances (RF1) can besubstantially canceled in relation to a module substrate for mountingthe waveguide type power detecting element (power sensor element) 210 asshown in FIG. 24.

[0319] That is, FIGS. 25A and 25B are schematic views in which thewaveguide type power detecting element (power sensor element) 210 asshown in FIG. 24 is mounted on the fin line module substrate 231 a and231 b used to match with the waveguide.

[0320] The material of these fin line module substrates 231 a and 231 bis alumina, and their thickness is 0.05 to 0.1 mm.

[0321] The fin line module substrates 231 a and 231 b have fin lineelectrodes for exponentially changing the impedance, in order tosmoothly match with the impedance of the waveguide.

[0322] In each of these fin line module substrates 231 a and 231 b, theentrance opening of the fin line electrode is substantially level withthe waveguide, and its exit opening is 0.4 mm, meeting the taper of thewaveguide type power detecting element 210.

[0323]FIG. 25A shows the fin line module substrate 231 a having norecess for compensation in the fin line electrode.

[0324]FIG. 25B shows the fin line module substrate 231 b having a recessfor compensation in the fin line electrode.

[0325] That is, the fin line module substrate 231 a or 231 b shown inFIG. 25B has a recess 232 formed in a portion close to the waveguidetype power detecting element (power sensor element) 210, with thiswaveguide type power detecting element (power sensor element) 210mounted.

[0326] More specifically, the fin line module substrate 231 a or 231 bshown in FIG. 25B produces reflection with reflectance RF2 at the twoend faces of the recess 232 owing to changes in the impedance, with thewaveguide type power detecting element (power sensor element) 210mounted.

[0327] By properly determining the shape and size (which determine theimpedance) of the recess 232 and the distance (which determines thephase difference) between the recess 232 and the waveguide type powerdetecting element (power sensor element) 210, the absolute value of thereflection with the reflectance RF1 produced in the waveguide type powerdetecting element (power sensor element) 210 and the absolute value ofthe reflection with the reflectance RF2 produced in the fin line modulesubstrate 231 b can be set to be substantially equal to each other, andthe phase difference can be set to 180°.

[0328] That is, the reflection with the reflectance RF1 produced in thewaveguide type power detecting element (power sensor element) 210 can becanceled by the reflection with the reflectance RF2 produced in the finline module substrate 231 b.

[0329]FIGS. 26A and 26B show the measurement results of an SWR in the Vband (50 to 75 GHz) and the X band (75 to 110 Hz), respectively, of thewaveguide type power detecting device constructed as above.

[0330] As shown in FIGS. 26A and 26B, in either of the V band (50 to 75GHz) and the X band (75 to 110 Hz), the SWR produced in this waveguidetype power detecting device with compensation indicated by the solidline is smaller than that produced without compensation indicated by thebroken line. That is, in either case the performance greatly improved.

[0331]FIG. 27 is a view showing the way the waveguide type powerdetecting device constructed as above is packaged.

[0332] The fin line module substrate 231 b mounting the waveguide typepower detecting element (power sensor element) 210 is packaged as it issandwiched between waveguide cases 233 a and 233 b, split into two partsas casings.

[0333] Referring to FIG. 27, an input terminal (WR15 flange) 234 formillimeter-wave signals is formed in the front portion, and sensoroutput terminals (two DC terminals) 236 are formed in the rear portion.

[0334] Also, in FIG. 27 a BNC coaxial input terminal 237 for inputting acalibration signal is formed on one side.

[0335] The material of the waveguide cases 233 a and 233 b, split intotwo parts as casings, is gold-plated brass (outer dimensions=70×24×24mm).

[0336] The casings for the two, V and W, bands have the same outerdimensions, and the dimensions of their inner waveguides are (3.76×1.88mm) and (2.54×1.27 mm), respectively.

[0337] The dimensional accuracy, angular accuracy, surface roughness,and packaging of these casings were improved. As a consequence, thereflectance of the waveguide itself decreased to 0.05 or less.

[0338] (Sixth Embodiment)

[0339]FIGS. 28A and 28B show a waveguide type wide-band RF signal powerdetecting device (power sensor) according to the sixth embodiment of thepresent invention.

[0340] As a waveguide type wide-band RF signal power detecting element(power sensor element) 254, the waveguide type wide-band RF signal powerdetecting element (power sensor element) realized in the fifthembodiment described above is used.

[0341] As shown in FIGS. 28A and 28B, the power sensor of thisembodiment comprises a waveguide connector 251, a module casing 252, afin line module 253, the power sensor element 254, and a lead line 255.The waveguide connector 251 connects a waveguide (not shown) to thepower sensor to guide a signal to be measured propagating in thewaveguide to the power sensor. The module casing 252 has awaveguide-shaped hollow portion capable of propagating a signal to bemeasured. The fin line module substrate 253 is formed in a portion ofthe waveguide-shaped hollow portion in the module casing 252 and isanalogous to that in the fifth embodiment. The power sensor element 254is formed on this fin line module substrate 253. The lead line 255guides an output signal from this power sensor element 254 to adedicated meter.

[0342] A signal to be measured propagating in the waveguide (not shown)propagates in the waveguide-shaped hollow portion of the module casing252, propagates in a fin line electrode formed on the fin line modulesubstrate 253, and is concentrated to be narrowed to the center of thisfin line electrode.

[0343] The RF signal to be measured thus concentrated to the center ofthe fin line electrode is absorbed by a resistor of the power sensorelement 254 mounted on the fin line module substrate 253 and convertedinto heat.

[0344] The magnitude of the generation of heat by the conversion isdirectly proportional to the magnitude of the power of the supplied RFsignal to be measured.

[0345] The magnitude of the heat generation is converted into DC voltageby using a thermocouple placed close to the resistor.

[0346] This DC voltage is supplied to the dedicated meter via the leadline and displayed to indicate the magnitude of the power of the RFsignal to be measured.

[0347] Note that a connector (not shown) for supplying a calibrationsignal (DC or 1-MHz RF signal) is formed in a portion of the modulecasing 252.

[0348] To minimize reflection of a signal to be measured propagating inthe waveguide-shaped hollow portion of the module casing 252, i.e., tomeasure the signal with high accuracy, the fin line module substrate 253is placed parallel to the longitudinal direction of the waveguide-shapedhollow portion.

[0349] A signal to be measured propagates in the TE mode in thewaveguide. Hence, the fin line module substrate 253 placed in thewaveguide-shaped hollow portion of the module casing 252 is set parallelto the longitudinal direction of the waveguide-shaped hollow portion andperpendicular to the longitudinal direction of the section of the hollowportion, in order to minimize reflected waves.

[0350] To increase the detection sensitivity it is important for thisfin line module substrate 253 to maximize a signal supplied from asignal to be measured propagating in the waveguide-shaped hollow portionof the module casing 252.

[0351] Accordingly, the fin line module substrate 253 is placed parallelto the longitudinal direction of the waveguide-shaped hollow portion ofthe module casing 252 and perpendicular to the longitudinal direction ofthe section of the hollow portion. Additionally, the fin line modulesubstrate 253 is positioned in ⅓ portions of the distances from thecenters in the longitudinal directions.

[0352] To facilitate packaging the fin line module substrate 253 in themodule casing 252, this module casing is desirably constructed of twocomplementary waveguide casings 252 a and 252 b.

[0353] To suppress reflected waves, the height of projections on thesurfaces of the inner walls of the waveguide-shaped hollow portion ofthe module casing 252 is desirably very small, e.g., 3 μm or less.

[0354] The material of this module casing 252 is desirably copper orbrass having high electrical thermal conductivity. However, it is alsoeffective, to decrease the cost, to use plastic having a small linearexpansion coefficient as a base material and to cover the surface withplating of an electrically, thermally conductive material, such as goldor nickel.

[0355] As the fin line module substrate 253, sapphire or aluminum havinga large dielectric constant and a small dielectric loss is used.

[0356] As a method of mounting the power sensor element on this fin linemodule substrate 253, a solder fusing method is used.

[0357] To absorb electromagnetic waves leaking outside the surface ofthe module substrate 253 or to absorb a signal to be measured which isleft unabsorbed, a thin-film absorber or an electromagnetic waveabsorber, such as polyiron, is desirably placed, or charged, behind thepower sensor element, in order to increase the accuracy with which thesignal is measured.

[0358] In each of the above embodiments, heat generated in the resistorcan be efficiently conducted to the thermocouple when the substrate orthe module substrate is made of a high-heat-conductivity material.

[0359] To efficiently conduct heat generated in the resistor to thethermocouple, a high-heat-conductivity material can also be interposedbetween the resistor and the thermocouple.

[0360] As has been described above, in the first power detecting elementof the present invention, one end of a thin-film resistor formed on aninsulating substrate is connected to an input electrode formed at oneend of the substrate. The other end of this thin-film resistor isconnected to a ground electrode formed at the same end of the substrate.A thin-film thermocouple is formed in the vicinity of the thin-filmresistor to form a indirect heating structure in which the resistor andthe thermocouple are separated. The transmission impedance between afirst connecting portion connecting with the input electrode andconnecting the input electrode to the thin-film resistor and a secondconnecting portion connecting with the ground electrode and connectingthe ground electrode to the thin-film resistor is held at apredetermined value.

[0361] Accordingly, the size of the thin-film resistor can be decreasedindependently of the thermocouple. Additionally, the upper limit of themeasurement frequency can be greatly increased because the transmissionimpedance viewed from the input electrode and the ground electrode canbe well approached to the resistance of the thin-film resistor.

[0362] In the second power detecting element of the present invention,the thin-film resistor is made smaller than the input electrode and theground electrode, and the first connecting portion is widened toward theinput electrode. This facilitates mounting the power detecting element.

[0363] In the third power detecting element of the present invention,the ground electrode and the second connecting portion are so formed asto sandwich the input electrode and the first connecting portion. Thisallows the use of a coplanar transmission line. Also, since matching canbe easily obtained with respect to the resistance of the thin-filmresistor small in size, the upper limit of the measurement frequency canbe greatly increased.

[0364] The fourth power detecting element of the present invention hastwo thin-film resistors. This improves the heat resistance and allowsmeasurements of large power.

[0365] The fifth power detecting element of the present invention has astructure in which all members are formed using thin films on thesubstrate. Since this allows easy manufacture, it is possible to provideelements having uniform characteristics inexpensively. A coplanartransmission line is formed by making the ratio of the width of theinput electrode and the first connecting portion to the gap between theground electrode and the second connecting portion substantiallyconstant. Accordingly, the transmission impedance between the inputelectrode and first connecting portion and the ground electrode andsecond connecting portion can be easily matched with the resistance ofthe thin-film resistor. Consequently, the upper limit of the measurementfrequency can be greatly increased.

[0366] In the sixth power detecting element of the present invention,the thin film resistor and one member of the thermocouple are made of amicro-crystalline silicon germanium thin film. This further facilitatesthe manufacture, stabilizes the operation, and raises the burnout level.Therefore, highly accurate power detection can be performed.

[0367] In the seventh power detecting element of the present invention,a plurality of substantially fan-shaped thermocouples are radiallyarranged around the thin-film resistor on one surface of the substrate,and these thermocouples are connected in series. Accordingly, a largenumber of thermocouples can be formed in the limited substrate area, andmicro watt power can be measured.

[0368] In the first power detecting device of the present invention, thetransmission impedance of a central conductor and a ground conductor forguiding a signal to be measured to a power detecting element mounted ona module substrate is made substantially equal to the transmissionimpedance between electrodes of the power detecting element. Also, thecentral conductor is given an inductance component corresponding to acapacitance component increased by junctions between mounting portionsand the electrodes of the power detecting element. It is, therefore,possible to cancel the capacitance increased by the junctions betweenthe mounting portions and the electrodes of the power detecting element.Additionally, a signal to be measured guided by the central conductorand the ground conductor can be input to a resistor of the powerdetecting element in a matched state over a broad frequency range. So,the frequency characteristic of the power detecting element can be wellbrought out, and the upper-limit detection frequency of the whole devicecan be greatly extended.

[0369] Note that the present invention includes the following forms as acoaxial type wide-band RF signal power detecting element (power sensorelement), a waveguide type wide-band RF signal power detecting element(power sensor), and a power detecting device using the same.

[0370] (1) A wide-band RF signal power detecting element comprising

[0371] an insulating substrate,

[0372] at least one thin-film resistor formed on the substrate to absorbpower of a signal to be measured and generate heat,

[0373] first and second ground electrodes formed by thin-filmconductors, adjacent to an edge of the substrate, and separated fromeach other,

[0374] a first thin-film connecting portion formed on the substrate toelectrically connect-the first ground electrode to the at least onethin-film resistor,

[0375] a second thin-film connecting portion formed on the substrate toelectrically connect the second ground electrode to the at least onethin-film resistor, and made to narrow a gap between the first andsecond thin-film connecting portions toward the at least one thin-filmresistor,

[0376] an input electrode formed adjacent to the edge of the substrateand between the first and second ground electrodes,

[0377] an input connecting portion connected to the at least onethin-film resistor, with the at least one thin-film resistor interposedbetween the first and second thin-film connecting portions, toelectrically connect the input electrode to the at least one thin-filmresistor, such that a width of the input connecting portion decreasesfrom the input electrode toward the at least one thin-film resistor, andthat gaps between the input connecting portion and the first and secondthin-film connecting portions narrow toward the at least one thin-filmresistor, and

[0378] a thin-film thermocouple formed away from the at least onethin-film resistor with a predetermined gap between them to detect atemperature rise of the at least one thin-film resistor.

[0379] (2) A wide-band RF signal power detecting element described initem (1) above, characterized in that the at least one thin-filmresistor, the first and second ground electrodes, the first and secondthin-film connecting portions, the input electrode, and the inputconnecting portion form a coplanar transmission line.

[0380] (3) A wide-band RF signal power detecting element described initem (1) above, characterized in that the at least one thin-filmresistor, the first and second ground electrodes, the first and secondthin-film connecting portions, the input electrode, and the inputconnecting portion form a coplanar transmission line, and are so formedas to be equal to transmission impedance of a coaxial cable forpropagating the signal to be measured.

[0381] (4) A wide-band RF signal power detecting element described initem (1) above, characterized in that the first and second thin-filmconnecting portions are narrowed.

[0382] (5) A wide-band RF signal power detecting element described initem (1) above, characterized in that

[0383] the at least one thin-film resistor comprises a first thin-filmresistor having first and second terminals and a second thin-filmresistor having third and fourth terminals,

[0384] the first thin-film connecting portion is connected to the firstterminal of the first thin-film resistor,

[0385] the second thin-film connecting portion is connected to thefourth terminal of the second thin-film resistor, and

[0386] the input thin-film connecting portion is connected to the secondterminal of the first thin-film resistor and the third terminal of thesecond thin-film resistor.

[0387] (6) A power detecting device comprising

[0388] a power detecting element comprising

[0389] an insulating substrate,

[0390] at least one thin-film resistor formed on the substrate to absorbpower of a signal to be measured and generate heat,

[0391] first and second ground electrodes formed by thin-filmconductors, adjacent to an edge of the substrate, and separated fromeach other,

[0392] a first thin-film connecting portion formed on the substrate toelectrically connect the first ground electrode to the at least onethin-film resistor,

[0393] a second thin-film connecting portion formed on the substrate toelectrically connect the second ground electrode to the at least onethin-film resistor, and made to narrow a gap between the first andsecond thin-film connecting portions toward the at least one thin-filmresistor,

[0394] an input electrode formed adjacent to the edge of the substrateand between the first and second ground electrodes,

[0395] an input connecting portion connected to the at least onethin-film resistor, with the at least one thin-film resistor interposedbetween the first and second thin-film connecting portions, toelectrically connect the input electrode to the at least one thin-filmresistor, such that a width of the input connecting portion decreasesfrom the input electrode toward the at least one thin-film resistor, andthat gaps between the input connecting portion and the first and secondthin-film connecting portions narrow toward the at least one thin-filmresistor, and

[0396] a thin-film thermocouple formed away from the at least onethin-film resistor with a predetermined gap between them to detect atemperature rise of the at least one thin-film resistor, and

[0397] a module substrate made larger than the substrate of thewide-band RF signal power detecting element, and comprising a centralconductor and a ground conductor formed by patterning on one surface ofthe module substrate to guide a signal to be measured, and mountportions formed, in one-to-one correspondence with the electrodes of thewide-band RF signal power detecting element, at a distal end of thecentral conductor and in a portion of the ground conductor in thevicinity of the distal end of the central conductor, the modulesubstrate fixing the wide-band RF signal power detecting element to theone surface with the electrodes of the power detecting element joined tothe mount portions, supplying a signal to be measured to between theelectrodes of the wide-band RF signal power detecting element, andoutputting a signal corresponding to power of the signal to be measured,

[0398] characterized in that transmission impedance between the centralconductor and the ground conductor of the module substrate is madesubstantially equal to transmission impedance between the electrodes ofthe wide-band RF signal power detecting element, and the centralconductor is given an inductance component corresponding to acapacitance component increased by junctions between the mount portionsand the electrodes of the wide-band RF signal power detecting element.

[0399] (7) A wide-band RF signal power detecting device described initem (6) above, characterized in that at least one of the substrate andthe module substrate is made of a high-heat-conductivity substrate.

[0400] (8) A wide-band RF signal power sensor comprising

[0401] a module tube,

[0402] a module substrate inserted into the center of the module tube,

[0403] a power sensor element mounted on the module substrate, and

[0404] a lead line for extracting a signal from the power sensorelement.

[0405] (9) A wide-band RF signal power sensor described in item (8)above, characterized in that a hollow portion of the module tube isfilled with an electromagnetic absorber.

[0406] (10) A wide-band RF signal power sensor described in item (8)above, characterized in that the module substrate has a coplanarstructure.

[0407] (11) A wide-band RF signal power sensor described in item (8)above, characterized in that at least one of the substrate and themodule substrate is made of a high-heat-conductivity substrate.

[0408] (12) A wide-band RF signal power detecting element comprising

[0409] an insulating substrate,

[0410] a thin-film resistor formed on the substrate, such that a distalend portion has a predetermined inclination angle to an axial line, toabsorb power of a signal to be measured and generate heat,

[0411] first and second ground electrodes formed by thin-filmconductors, adjacent to an edge of the substrate, and separated fromeach other,

[0412] a first thin-film connecting portion formed on the substrate toelectrically connect the first ground electrode to the thin-filmresistor, and

[0413] a second thin-film connecting portion formed on the substrate toelectrically connect the second ground electrode to the thin-filmresistor, made to narrow a gap between the first and second thin-filmconnecting portions toward the thin-film resistor, and connected to thethin-film resistor with the thin-film resistor interposed between thefirst and second thin-film connecting portions.

[0414] (13) A wide-band RF signal power sensor characterized bycomprising

[0415] a waveguide connector for guiding a signal propagating in awaveguide to a power sensor,

[0416] a module casing including a waveguide type hallow portion,

[0417] a fin line module substrate formed in a portion of the hollowportion of the module casing,

[0418] a power sensor element formed on the fin line module substrate,and

[0419] a lead line for guiding an output signal from the power sensorelement to a dedicated meter.

[0420] (14) A wide-band RF signal power sensor described in item (13)above, characterized in that the fin line module substrate is setparallel to a longitudinal direction of the waveguide-shaped hollowportion.

[0421] (15) A wide-band RF signal power sensor described in item (13)above, characterized in that the fin line module substrate is setparallel to the longitudinal direction of the waveguide-shaped hollowportion and perpendicular to a longitudinal direction of a section ofthe waveguide-shaped hollow portion.

[0422] (16) A wide-band RF signal power sensor described in item (13)above, characterized in that the fin line module substrate is setparallel to the longitudinal direction of the waveguide-shaped hollowportion and perpendicular to a longitudinal direction of a section ofthe waveguide-shaped hollow portion, and is placed in ⅓ portions fromcenters in the longitudinal directions.

[0423] (17) A wide-band RF signal power sensor described in item (13)above, characterized in that the module casing is constructed ofcomplementary separate casings.

[0424] (18) A wide-band RF signal power sensor described in item (13)above, characterized in that the fin line module substrate has a recessby which absolute values of reflection produced in the power sensorelement and reflection produced in the fin line module substrate aresubstantially equal to each other, and a phase difference between themis substantially 180°.

[0425] As has been described in detail above, the present invention canprovide a wide-band RF signal power detecting element which is easy tomanufacture, has a high upper-limit detection frequency, can detectpower from direct current, and has a frequency characteristic notinfluenced by the number of thermocouples.

[0426] The present invention can also provide a power detecting deviceusing a wide-band RF power detecting element which is easy tomanufacture, has a high upper-limit detection frequency, can detectpower from direct current, and has a frequency characteristic notinfluenced by the number of thermocouples.

1. A wide-band RF signal power detecting device comprising: a wide-bandRF signal power detecting element comprising a substrate, a resistorformed on said substrate, electrodes formed on one surface of saidsubstrate and connected to two ends of said resistor, and a thermocouplefor outputting a signal corresponding to heat generated by saidresistor, and set such that transmission impedance between saidelectrodes has a predetermined value; and a module substrate made largerthan said substrate of said wide-band RF signal power detecting element,and comprising a central conductor and a ground conductor formed bypatterning on one surface of said module substrate to guide a signal tobe measured, and mount portions formed, in one-to-one correspondencewith said electrodes of said wide-band RF signal power detectingelement, at a distal end of said central conductor and in a portion ofsaid ground conductor in the vicinity of the distal end of said centralconductor, said module substrate fixing said wide-band RF signal powerdetecting element to the one surface with said electrodes of said powerdetecting element joined to said mount portions, supplying a signal tobe measured to between said electrodes of said power detecting element,and outputting a signal corresponding to power of the signal to bemeasured, wherein a transmission impedance between said centralconductor and said ground conductor of said module substrate is madesubstantially equal to a transmission impedance between said electrodesof said wide-band RF signal power detecting element, and wherein saidcentral conductor is given an inductance component corresponding to acapacitance component increased by junctions between said mount portionsand said electrodes of said wide-band RF signal power detecting element.2. A device according to claim 1, wherein the inductance componentcorresponding to the increased capacitance component is formed in thevicinity of said mount portion of said central conductor.